1. Field of the Invention
The present invention relates to an apparatus and method for measurement of a physiologic function. In particular, the present invention relates to a noninvasive medical instrument for noninvasive measurement of physiologic characteristics based upon the monitoring of heartbeats and respiratory cycle in order to determine quantitatively the respiratory sinus arrhythmia (RSA).
2. Description of the Prior Art
In my U.S. Pat. No. 4,519,395 entitled "Medical Instrument for Noninvasive Measurement of Cardiovascular Characteristics", which issued May 28, 1985, I described an apparatus and method which provided a precise and highly reproducible quantitative measurement of sinus arrhythmia. The apparatus described in my U.S. Pat. No. 4,519,395 uses a pulse transducer to provide signal pulses representative of sensed heartbeats of the human subject. Stimuli are provided to the human subject as a function of the signal pulses in order to permit the human subject to voluntarily synchronize the subject's respiratory cycles with the heartbeats. In this way, each respiratory cycle corresponds to a predetermined number of heartbeats.
The apparatus described in my U.S. Pat. No. 4,519,395 determines instantaneous heart rate for each beat of the end beat voluntarily synchronized respiratory cycles based upon the time interval between signal pulses and sorts the instantaneous heart rate data by beat. A digital computer analyzes the sorted digital data and derives one or more digital values which are indicative of a characteristic of the subject's cardiovascular system. This data analysis preferably includes rhythmometric, statistical, and arithmetic analyses based upon the sorted digital data.
Using the apparatus of my U.S. Pat. No. 4,519,395, it is possible to provide a highly sensitive quantitative measurement of sinus arrhythmia parameters. As described in my patent, these parameters provide information which is useful in the quantification of physiologic cardiovascular age. The effects of toxins, cardiac drugs, hormones and aerobic exercise (or other forms of cardiovascular training) and the status of various cardiovascular or pulmonary disease states can also be monitored using this medical instrument.